1. Field of the Invention
This invention relates to a three-dimensional image (hereinafter referred to as 3-D image) forming method on thermally expansible sheets.
2. Description of the Related Art
As set forth in Japanese Examined Patent Publication (KOKOKU) No. 35359/1984, the following 3-D image forming method has been known: A predetermined image is formed on a thermally expansible sheet with an image forming material of a high light absorbing ability, and light is irradiated on the thermally expansible sheet. Then, only the image portions are selectively heated and protruded by the difference in the light absorbing abilities. Whereby the 3-D image has been formed.
The conventional 3-D image forming method employs the image forming material which satisfies the high light absorbing ability requirement. The 3-D image forming method accordingly employs a black or brown image forming material. Therefore, no 3-D image can be obtained when the predetermined image is formed on the thermally expansible sheet with a red, blue, green or yellow image forming material. This is because such image forming material has low light absorbing abilities.
When one desires to color the 3-D image thus obtained, foils of a desired color are transferred on the 3-D image portions However, the number of the operation processes increases and the operation becomes complicated because the transferring should be done after the 3-D image forming. In addition, when the color foils are transferred on the image portions in black without completely covering the neighboring portions of the image portions, the appearance of the 3-D image deteriorates because the color of the thermally expansible sheet is exposed.